Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., frequency/time resources). Examples of such multiple-access technologies include time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, code division multiple access (CDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of a telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards preferably using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and increasingly using MIMO antenna technology.
MIMO technology has matured for wireless communication systems and has been incorporated into wireless broadband standards such as LTE and Wi-Fi. Basically, the more antennas that the transmitter/receiver is equipped with, the greater the possible signal paths and the better the performance in terms of data rate and link reliability.
Massive MIMO also known as large-scale antenna systems, very large MIMO, hyper-MIMO and full-dimension (FD) MIMO makes a break with current MIMO practice through the use of a very large number of service antennas (e.g., hundreds or even thousands) that are operated fully coherently and adaptively. The very large number of antennas help by focusing the transmission and reception of signal energy into ever-smaller regions of space. This brings huge improvements in throughput and energy efficiency, in particular when combined with simultaneous scheduling of a large number of user terminals (e.g., tens or hundreds). Massive MIMO was originally envisioned for time division duplex (TDD) operation, but can be applied also in frequency division duplex (FDD) operation. Other benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency, simplification of the media access control (MAC) layer, and robustness to interference and intentional jamming.
U.S. Pat. No. 8,855,002 discloses an apparatus for feeding back channel information to a base station (BS) connected to one or more User Equipments (UEs). The apparatus generates and feeds back CSI considering inter-UE interference due to an access of an additional UE. The feedback apparatus comprises a CSI reference signal (CSI-RS) receiver for receiving a CSI-RS from the BS, a channel estimator for estimating a channel by using the received CSI-RS, a demodulation RS (DM-RS) receiver for receiving a DM-RS of the additional UE, a precoder estimator for estimating a type of a precoder (PC) of the corresponding additional UE based on the received DM-RS of the additional UE and a channel estimation result by the channel estimator, a Multiple Access Interference (MAI) determiner for determining MAI based on information on the precoder of the additional UE estimated by the precoder estimator and the channel estimation result by the channel estimator, and a state information generating/transmitting unit for generating and feeding back CSI reflecting interference generated due to the additional UE according to the MAI.
WO2008147121 relates to MIMO feedback and transmission in a wireless communication system. It discloses a method of selecting a subset codebook or full code book based on traffic load of a BS, and broadcasting the selected codebook to UEs. In high traffic load, a subset codebook is selected, and in low traffic load, a full codebook is selected. UEs calculate a channel quality indicator (CQI) of a spatial codeword vector that is included in the selected codebook. Information of the maximum CQI is sent to the BS together with a precoder of the UE. The BS selects UEs based on the information of the maximum CQI and precoder, and transmits the preferred precoder signal and data signal to the UEs.
U.S. Pat. No. 9,485,661 discloses a method of facilitating the generation and use of separable, hierarchical channel state feedback in a wireless communication system. In the event that multiple network nodes, e.g. access points, cooperate to conduct DL transmissions to a UE, channel state feedback as reported by the UE can be separated into intra-node feedback relating to per-node channel conditions and inter-node feedback relating to relative phase and/or amplitude between channels corresponding to respective nodes. Further, a UE can select to report intra-node feedback and/or inter-node feedback based on network instructions, a cooperation strategy to be utilized by respective network nodes, or the like. Respective codebooks on which inter-node and intra-node channel feedback is based can be configured to convey information relating to a partial channel description and/or to vary based on resource units (e.g., sub-bands, resource blocks, etc.) utilized for DL communication. More specifically, the disclosed method involves analyzing parameters relating to a mobility of an associated UE, e.g. cellular telephone, and network back-haul conditions. A DL coordination strategy is selected to be utilized across the network nodes for communication with the associated UE based on the analyzed parameters. The associated UE is instructed to provide a per-node channel state feedback and an inter-node channel state feedback based on the selected DL coordination strategy. The feedbacks are received from the associated UE unit.
US2013/0163544 discloses a method in a massive MIMO wireless communication system of beamforming and information feedback. Signals for beams to be transmitted through corresponding antenna ports of a BS, are generated. The beams are formed by precoding the signals with beamforming vectors. The beams are sorted into a number of resource reuse groups based on a resource that is to be shared. The beams are transmitted, using resources allocated per group, to a UE. Feedback information is generated at the UE on at least one antenna port, based on the received beams. The feedback information is transmitted to the BS. A beam is selected having a greatest gain for a BS using the feedback information. A transmission resource is allocated for the selected beam.
One of the major changes from Fourth Generation (4G) or LTE to Fifth Generation (5G) massive MIMO mobile network (wireless) communication systems is, as indicated above, the number of antennas in each BS or transmission reception point (TRP). The number of antennas for 4G/LTE is typically less than 16 antennas per BS (up to Release 13), where the number of antennas for 5G massive MIMO is typically more than 100 antennas per BS and could be as many as thousands. As there are 100 or more antennas within a BS, the beam width of each antenna can be much narrower. Nonetheless, the probability of channel blockage due to narrow beam width will be increased. Therefore, a method of selecting one or more subsets of antennas to provide optimal throughput is very desirable.